Project Summary/Abstract (Lay/Scientific Summary, limit 30 lines) Non-motile primary cilia are organelles found on the surface of most cells where they play pivotal sensory and signaling roles required for normal human development and organ function. Defects in cilia assembly or function can lead to multiple human pathologies, collectively known as ciliopathies, including polycystic kidney disease and several other syndromes. Primary endothelial cilia are mechanosensory organelles that are projected into the lumen of blood vessels. It has been demonstrated that vascular endothelia require primary cilia to sense and transmit external mechanical stimuli into internal biochemical reactions. One of these reactions includes the biosynthesis and release of nitric oxide, which is one of the most potent endogenous vasodilators. This idea has only been investigated in cultured endothelial cells in vitro. Based on this finding, however, a very bold hypothesis is formed to test that abnormal cilia function results in vascular hypertension. New and surprising data that were recently generated by the PI show that muscarinic acetylcholine receptors, which has been known to regulate blood pressure and cell division, are localized to primary cilia and can modulate cilia length and function. Because there is a positive and continuous correlation between blood pressure and renal diseases, satellite hypotheses are developed to look at the pathophysiological roles of epithelial ciliary muscarinic receptors in renal function and consequently hypertension in vivo. This project will therefore utilize state-of-the art approaches to test these highly innovative concepts. A series of conditional mouse models will be used, coupled with high-resolution microscopy techniques. In Aim 1, we will use vascular-specific mouse models of Pkd1, Tg737 and AChM3R to study systolic/diastolic blood pressure. The expression and localization of muscarinic receptors will be investigated in primary cilia dysfunction (PKD). Moreover, the function of ciliary AChM3R will be analyzed in vivo. We will study the mechanism of Cilia-Pkd1- AChM3R, including blood pressure control in matured adult vascular system. Most importantly, we will test a pharmacological intervention to reduce blood pressure in our animal models by bypassing cilia function. In Aim 2, we will study the expression and localization of AChM3R in normal and Pkd kidneys. We will also examine the kidney phenotype in AChM3R kidney-specific knockout mouse and study blood pressure in kidney- specific knockouts with normal vascular function. We will further test the idea to rescue the cystic kidney phenotype by pharmacological intervention to bypass ciliary polycystin. There is mounting evidence implicating calcium and cAMP as central players in a network of signaling pathways underlying the pathogenesis of PKD. The cellular and molecular mechanisms of cyst formation will be studied in AChM3R knockout renal epithelia. Overall, the proposed studies will fill a critical gap in our existing knowledge by providing novel information on the physiology of ciliary AChM3R and will advance the larger field of primary cilia signaling particularly in relation to blood pressure control and kidney function.